Referring to FIG. 1, a conventional MR imaging apparatus comprises an NMR scanner 10 having a coil in which a signal containing information regarding the object being scanned is produced. An amplifier 11, coupled to the NMR scanner 10, strengthens the information signal. A local oscillator 13 provides a signal having a predetermined frequency to a mixer 12 which is coupled to the amplifier 11. The mixer 12 shifts the frequency of the information signal, preferably downwardly, by the frequency of the signal provided by the local oscillator 13. A filter 14, coupled to the mixer 12, passes the interval of frequencies of the information signal which contain the relevant data. An analog-to-digital converter 15, coupled to the filter 14, converts the filtered signal into digital form. A computer 16, coupled to the analog-to-digital converter 15, generates an image of the object being scanned from the digital signals provided by the analog-to-digital converter 15.
The signals in the apparatus contain noise, which ultimately detracts from the clarity of the image created by the computer 16. Specifically, noise in the signals engenders a grainy quality in any resulting image. Present MR imaging apparatus exhibit the limitations in the quality of images owing to noise in the signals.
Accordingly, reduction in noise in such apparatus is highly desirable to enhance the clarity of images.